It is strictly forbidden to wear a full suit of armor inside the Houses of Parliament.

Trouble-o-Meter
Modern police would just stop you at the door.

Status: technically enforceable

Why Is This a Law?

In 1313, furious noblemen kept showing up to Parliament wearing battle armor and carrying swords to intimidate King Edward II. To stop the bullying, the King banned armor in parliament.

A citizen earnestly dealing with the law: It is strictly forbidden to wear a full suit of armor inside the Houses of Parliament.